Cassettes of the type disclosed in U.S. Pat. No. 5,928,934 and 5,665,398, the disclosures of which are incorporated herein by reference in their entireties, are used to store, treat, and hold tissue samples in preparation of performing microscopic histological examination of such tissue. Typically, a cassette comprises a receptacle portion that forms a cavity and a lid. The receptacle and lid each typically have numerous small apertures that allow fluid to pass through the cassette and into the cavity. The lid is often attached to the receptacle by a hinge in a manner such that the lid can be used to selectively open and close the cavity of the receptacle.
During the treatment of a tissue sample in preparation of microscopic examination, the tissue sample is typically placed in the cavity of a cassette with the lid of the cassette closed to prevent the tissue sample from inadvertently falling out of the cavity. The cassette is then typically immersed in sequence any number of various fluids such as formaldehyde, ethanol, xylene, and molten paraffin. The apertures in the receptacle and lid of the cassette allow such fluids to pass into the cavity of the cassette and make contact with the tissue sample. In the timing of these steps, a tissue sample is dehydrated, cleared and infiltrated with molten wax within the cassette. Multiple tissue samples in multiple cassettes can be treated in this manner simultaneously.
The treatment procedures typically concludes with the tissue sample resting in molten paraffin. The lid of the cassette is thereafter opened and the tissue sample is removed from the cassette and placed in the cavity of an embedding mold. The cassette is then placed above the tissue sample in the embedding mold and additional paraffin is used to secure the tissue sample to the bottom surface of the cassette. This additional paraffin is allowed to solidify in and around the apertures of the receptacle and thereby provides a firm attachment of the tissue sample to the cassette. As such, the cassette can then be used to hold the wax infiltrated tissue sample as an investment casting of the tissue sample to be sliced by a microtome.